linux-kernel - Re: [PATCH v2 4/4] Documentation: dt: bindings: add LP3943 bindings

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Date:	Wed, 14 Aug 2013 12:58:38 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	"Kim, Milo" <Milo.Kim@...com>
Cc:	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"lee.jones@...aro.org" <lee.jones@...aro.org>,
	"Samuel Ortiz (sameo@...ux.intel.com)" <sameo@...ux.intel.com>,
	"broonie@...nel.org" <broonie@...nel.org>,
	"linus.walleij@...aro.org" <linus.walleij@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>
Subject: Re: [PATCH v2 4/4] Documentation: dt: bindings: add LP3943 bindings

On Tue, Jul 30, 2013 at 12:42:29AM +0000, Kim, Milo wrote:
[...]
> diff --git a/Documentation/devicetree/bindings/gpio/gpio-lp3943.txt b/Documentation/devicetree/bindings/gpio/gpio-lp3943.txt
[...]
> +Required properties:
> +  - compatible: "ti,lp3943-gpio"
> +  - gpio-controller: device node as a GPIO controller

"Marks the device node as a GPIO controller"?

> +  - #gpio-cells: Should be two.

"Should be 2"?

[...]
> +		gpios = <&gpioex 9 1>;	/* active-low */
[...]
> +		gpios = <&gpioex 10 1>;	/* active-low */

If you use the defines as Lee suggested, then you don't need these
comments either.

> diff --git a/Documentation/devicetree/bindings/mfd/lp3943.txt b/Documentation/devicetree/bindings/mfd/lp3943.txt
> new file mode 100644
> index 0000000..ef62784
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/lp3943.txt
> @@ -0,0 +1,33 @@
> +TI/National Semiconductor LP3943 MFD driver
> +
> +Required properties:
> +  - compatible: "ti,lp3943"
> +  - reg: I2C slave address (u8). 0x60 ~ 0x67

u8 is a Linux specific and implementation detail. I think it's safe to
assume that everybody knows that I2C slave addresses are 7 bits (and
you even provide a valid range), so just drop the "(u8)".

> +lp3943@60 {
> +	compatible = "ti,lp3943";
> +	reg = <0x60>;
> +
> +	gpioex: gpio {
> +		compatible = "ti,lp3943-gpio";
> +		gpio-controller;
> +		#gpio-cells = <2>;
> +	};
> +
> +	pwm3943: pwm {
> +		compatible = "ti,lp3943-pwm";
> +		#pwm-cells = <3>;
> +		ti,pwm0 = < 8 9 10 >;

This should probably be written as "<8 9 10>" for consistency.

> diff --git a/Documentation/devicetree/bindings/pwm/pwm-lp3943.txt b/Documentation/devicetree/bindings/pwm/pwm-lp3943.txt
[...]
> +Required properties:
> +  - compatible: "ti,lp3943-pwm"
> +  - #pwm-cells: Should be three.

"Should be three"? Although since as I mentioned the chip doesn't
support polarity inversion, this should now be "2".

> +    1) index of PWM controller
> +       0 = PWM 0, 1 = PWM 1
> +    2) PWM signal period in nanoseconds
> +       min = 6250, max = 1600000
> +    3) bitmask of optional PWM polarity flags
> +       0 = normal, 1 = inversed

All of this can probably go away. The new way of doing this is to
reference the standard bindings document using something like the below:

  - #pwm-cells: Should be 2. See pwm.txt in this directory for a
                description of the cells format.

Since you have a restriction on the minimum and maximum period lengths,
you could add something like:

                Note that this hardware limits the period length to the
                range 6250-1600000.

> +  - ti,pwm0 or ti,pwm1: Output pin number(s) for PWM port 0 or 1.

"PWM port" -> "PWM channel"

> +    0 = invalid
> +    1 = output 0
> +    2 = output 1
> +    .
> +    .
> +    16 = output 15

I thought I read that this is now a 1:1 mapping?

> +Example:
> +PWM 0 is for RGB LED brightness control
> +PWM 1 is for brightness control of LP8557 backlight device
> +
> +&i2c3 {
> +	lp3943@60 {
> +		compatible = "ti,lp3943";
> +		reg = <0x60>;
> +
> +		/*
> +		 * PWM 0 : output 7, 8 and 9
> +		 * PWM 1 : output 15
> +		 */
> +		pwm3943: pwm {
> +			compatible = "ti,lp3943-pwm";
> +			#pwm-cells = <3>;
> +			ti,pwm0 = < 8 9 10 >;

And here as well: "< 8 9 10 >" -> "<8 9 10>".

Thierry

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